1. Field
Embodiments relate to a secondary battery.
2. Description of the Related Art
In general, in a secondary battery, an electrode assembly—in which a positive electrode plate, a negative electrode plate, and a separator interposed therebetween are wound in a jelly-roll configuration—may be housed in a can together with electrolyte. An opening at the upper end of the can may be sealed by a cap assembly. In a square type secondary battery, the can may take the form of a substantially parallelepipedal shaped metal container and may be formed by a machining method, e.g., deep drawing.
The cap assembly may include a cap plate coupled to an upper portion of the can, a gasket for insulating the cap plate at the outer surface of the cap plate, an electrode terminal inserted into a terminal through-hole formed in the cap plate, an insulation plate under the cap plate, and a terminal plate under the insulation plate and electrically connected to the electrode terminal. The negative electrode of the electrode assembly may be electrically connected to the electrode terminal, and the positive electrode of the electrode assembly may be electrically connected to the cap plate.
An insulation case insulating the electrode assembly and the cap assembly under the terminal plate may be attached to the upper surface of the electrode assembly and the lower surface of the cap assembly. In other words, the cap assembly may be insulated from the electrode assembly by the insulation case and may be coupled to the opening at the upper end of the can to seal the can.
When a physical impact is applied to a conventional secondary battery in a standard test, e.g., a drop test, the insulation case may be pressed downward by the cap plate; or the short edges of the insulation case may not be restored to their original state after the impact due to a protrusion on the lower surface of the cap plate. The insulation case may continuously press against the upper surface of the electrode assembly, which may cause a short circuit between the electrodes and which may cause deformation of the electrode assembly.